1. Field of the Invention
The present invention relates to a process for purifying a halogen-containing gas. More particularly, it pertains to a process for removing a hydrogen halogenide such as hydrogen chlorides hydrogen bromide and hydrogen fluoride as well as moisture that are contained as impurities in a halogen-containing gas as low as a ultralow concentration to provide a halogen gas or an inert gas-containing halogen gas each free from a hydrogen halogenide and moisture.
A halogen gas such as chlorine and fluorine and a gas containing the above-mentioned halogen gas (hereinafter sometimes collectively referred to as "halogen-containing gas") are employed in relatively large amounts for the etching of a single crystal silicon film, aluminum film and aluminum alloy film in a semiconductor manufacturing process. With the remarkable advance of the semiconductor manufacturing technique in recent years and at the present time, it is required that the aforesaid halogen-containing gas be ultralow in the content of impurities such as a hydrogen halogenide, moisture and the like.
2. Description of the Related Arts
A halogen-containing gas to be used in a semiconductor manufacturing process or the like is supplied usually in the form of being filled in a vessel such as a gas cylinder. A crude halogen-containing gas frequently contains about 5 ppm or more of a hydrogen halogenide, moisture and the like as an impurities, which is responsible for trouble due to the corrosion of manufacturing equipment such as gas supply piping and for the occurrence of off-specification products due to the etching of a semiconductor thin film.
It is thought that moisture among the aforestated impurities can be removed to some extent by bringing a moisture-containing gas into contact with a publicly known zeolite. In recent years, however, it has been made possible to highly purify silane as a principal raw material for manufacturing semiconductors by removing oxygen contained therein as an impurity as low as 0.01 ppm or less. (Refer to Japanese Patent Application Laid-Open No.12303/1991.) Likewise, it it desired that a halogen-containing gas to be used under the circumstance similar to the above be highly purified by removing hydrogen halogenide and moisture contained in the halogen-containing gas as impurities as low as the same level as above so as to attain the purpose of preventing corrosion and the occurrence of off-specification products.
In addition, there is the possibility of such impurities as moisture and air mixing in the above-mentioned raw material gas at the time of exchanging gas cylinders or switching supply piping during the course of supplying the gas to the semiconductor manufacturing equipment. Accordingly, it is desired to ultimately remove the impurities immediately before the raw material gas enters the manufacturing equipment.
Nevertheless, almost nothing has been found with regard to the technique capable of simultaneously or separately removing, in high efficiency, hydrogen halogenide and/or moisture contained as impurities in a halogen gas such as chlorine, fluorine or the like.